'cat' command for internal shell - Support Python 3

[chamalsl]

Summary

LLVM Bug Id : 36449

Revision 328563 caused tests to fail under python 3.

1. This patch modified cat.py file to support both python 2 and 3.
2. This patch also fixes CRLF issues on Windows.

[chamalsl]

I tried below code to reopen stdout in binary mode as suggested in https://reviews.llvm.org/D43501.
sys.stdout = os.fdopen(sys.stdout.fileno(),"wb")
This worked for both python 2 and python 3.
But I could not get it to fix Windows CRLF issue.

[chamalsl]

Modified the fix to get rid of ord function.

[rnk]

lgtm

utils/lit/lit/builtin_commands/cat.py

 import getopt
 import sys
 try:
     from StringIO import StringIO
 except ImportError:
     from io import StringIO
 
 def convertToCaretAndMNotation(data):
    newdata = StringIO()
    for char in data:
+       if isinstance(data, str):
            intval = ord(char)
+       else:
+           intval = char
        if intval == 9 or intval == 10:
            newdata.write(chr(intval))
            continue
        if intval > 127:
            intval = intval -128
            newdata.write("M-")
        if intval < 32:
            newdata.write("^")
            newdata.write(chr(intval+64))
        elif intval == 127:
            newdata.write("^?")
        else:
            newdata.write(chr(intval))
 
-   return newdata.getvalue();
+   return newdata.getvalue().encode()
 
 
 def main(argv):
     arguments = argv[1:]
     short_options = "v"
     long_options = ["show-nonprinting"]
     show_nonprinting = False;
 
     try:
         options, filenames = getopt.gnu_getopt(arguments, short_options, long_options)
     except getopt.GetoptError as err:
         sys.stderr.write("Unsupported: 'cat':  %s\n" % str(err))
         sys.exit(1)
 
     for option, value in options:
         if option == "-v" or option == "--show-nonprinting":
             show_nonprinting = True;
 
+    writer = getattr(sys.stdout, 'buffer', None)
+    if writer is None:
+        writer = sys.stdout
+        if sys.platform == "win32":
+            import os, msvcrt
+            msvcrt.setmode(sys.stdout.fileno(),os.O_BINARY)
     for filename in filenames:
         try:
             fileToCat = open(filename,"rb")
             contents = fileToCat.read()
             if show_nonprinting:
                 contents = convertToCaretAndMNotation(contents)
-            sys.stdout.write(contents)
+            writer.write(contents)
             sys.stdout.flush()
             fileToCat.close()
         except IOError as error:
             sys.stderr.write(str(error))
             sys.exit(1)
 
 if __name__ == "__main__":
     main(sys.argv)